How do you restrict the left click rate in the game engine?
You can create a timer property in the logic editor panel and name it whatever you want. Say - "dTimer". Now when your game runs it will run. And in your python script do like this -

if mouse_click.positive and own["dTimer"] &gt;= 2: #2 seconds
    #do whatever you want
    own["dTimer"] = 0 #Reset the counter to zero


As soon as you reset it to 0, it will start the counting from 0 again. You can debug the property if you want.